Tasmania’s giant kelp forests have declined by over 95% since the 1940s. South Australia’s kelp has retreated hundreds of kilometers northward. These underwater forests—as ecologically important as terrestrial forests—are being replaced by “urchin barrens,” areas where sea urchins have grazed kelp down to bare rock. Restoration is difficult, expensive, and uncertain. But several programs are showing it’s possible.

Why Kelp Forests Matter

Giant kelp (Macrocystis pyrifera) and other kelp species create three-dimensional habitat for hundreds of marine species. Fish, invertebrates, and seaweeds all depend on kelp forests. Commercial species like rock lobster and abalone rely on kelp habitat at some life stage.

Kelp also absorbs carbon dioxide, produces oxygen, and dampens wave energy that would otherwise erode coastlines. Economically, kelp forests support commercial fisheries worth hundreds of millions annually to Australia’s economy.

When kelp forests disappear, species diversity crashes. Urchin barrens are biological deserts—bare rock covered in sea urchins, with almost nothing else. The ecosystem services kelp provided are lost.

What’s Killing Australian Kelp

The primary driver is ocean warming. The East Australian Current has strengthened and extended southward, pushing warm water into areas that were historically cooler. Kelp tolerates only certain temperature ranges—above their threshold, kelp struggles to grow and reproduce.

Warm water also brings sea urchins (particularly the long-spined sea urchin, Centrostephanus rodgersii) into areas where they didn’t previously occur. These urchins graze kelp relentlessly. Without natural predators in their new range, urchin populations explode.

The combination is devastating. Warming stress weakens kelp. Urchins prevent any recovery by eating new kelp growth as soon as it appears. Once kelp is gone, bare rock and urchins remain.

Overfishing of urchin predators (rock lobster, large wrasses) exacerbates the problem. Historically, predators kept urchin numbers in check. With predators depleted, nothing controls urchin populations.

The Restoration Challenge

You can’t just replant kelp in urchin-dominated areas. The urchins will eat it. Restoration requires either removing urchins first or protecting young kelp until it grows large enough to withstand grazing.

Several approaches are being tested in Australia:

Urchin Culling Programs

The most direct approach is removing urchins. Divers manually collect or crush urchins, reducing populations enough for kelp to regrow. This works, but it’s labour-intensive and expensive.

Tasmania’s “Operation Crayweed” (primarily focused on Sydney, but techniques apply) demonstrated that urchin culling in combination with kelp transplants can restore kelp in small areas. After urchin removal, kelp regrew naturally from spores or transplanted adults established successfully.

The challenge is scale. You can cull urchins from a few hectares with volunteer divers, but Tasmania’s lost kelp forests span hundreds of square kilometres. Culling at that scale isn’t economically viable without substantial funding or commercial urchin harvesting.

Commercial Urchin Harvesting

Some programs are exploring commercial harvesting of urchins for the roe (uni) market. If urchin harvesting becomes profitable, commercial divers will remove urchins at scale, potentially allowing kelp recovery as a side benefit.

South Australia is trialing this approach. The long-spined sea urchin produces edible roe. If markets develop, the invasive urchin becomes a resource, and commercial pressure reduces urchin density.

The economics are uncertain. Processing costs are high, market demand fluctuates, and urchins from barrens often have poor-quality roe because they’re not eating high-quality food (kelp). But it’s a promising direction that could self-fund restoration.

Green Gravel: Kelp Spore Seeding

The “green gravel” technique developed in Norway and being adapted for Australia involves coating small stones with kelp spores and broadcasting them over restoration sites. The spores grow into young kelp attached to the gravel.

This bypasses the need to transplant adult kelp, which is expensive and labour-intensive. If urchin densities are reduced (but not eliminated), the sheer number of seeded kelp might overwhelm the urchins’ grazing capacity—enough survive to establish new forests.

Tasmanian trials are underway. Early results show kelp can establish from green gravel in areas with moderate (not extreme) urchin density. It’s not a silver bullet, but it’s a scalable technique that could work in combination with urchin management.

Predator Restoration

Restoring urchin predators—rock lobster, large wrasses—could create a natural urchin control system. This requires fishing closures and marine protected areas where predator populations can rebuild.

Tasmania and South Australia have established marine parks specifically to protect kelp habitat and rebuild predator populations. The theory is that recovered predator populations will naturally suppress urchins, allowing kelp to recover without constant human intervention.

This is a long-term strategy. Predator recovery takes years or decades. But it addresses the root ecological imbalance rather than just treating symptoms.

Assisted Adaptation

Some researchers are exploring whether kelp can adapt to warmer temperatures. This might involve selective breeding of heat-tolerant kelp strains, or translocating kelp from warmer regions that already tolerate higher temperatures.

The University of Tasmania’s Institute for Marine and Antarctic Studies is researching this. The goal is kelp populations that can survive in future ocean temperatures, not just current conditions.

This is controversial—it’s essentially engineering ecosystems. But with warming projected to continue, restoration with current kelp strains might just create forests that die again in a decade. Heat-adapted kelp could persist longer.

Community Involvement

Several restoration projects involve recreational divers and citizen scientists. The Reef Life Survey trains volunteers to conduct urchin culls and monitor kelp recovery. This builds public awareness and provides labour for restoration at a fraction of professional diver costs.

Community involvement also creates political support for marine protection policies. When hundreds of divers see urchin barrens firsthand and participate in restoration, they become advocates for kelp protection and fisheries management.

What Success Looks Like

Realistic success isn’t returning to 1940s kelp coverage—the ocean has warmed too much. Success is stabilizing kelp forests in areas where they can still tolerate temperatures, preventing further losses, and creating resilient populations that can adapt to ongoing change.

Small-scale restoration sites show this is possible. Kelp has been successfully restored in Sydney Harbour, in South Australian marine parks, and in trial sites around Tasmania. The challenge is scaling up and sustaining effort over decades.

How You Can Help

Support organizations doing kelp restoration. Operation Crayweed, The Nature Conservancy’s Australian kelp projects, and university research programs all need funding.

If you’re a diver in affected regions, join volunteer restoration programs. The Reef Life Survey, local marine conservation groups, and citizen science initiatives need skilled divers for surveys and urchin culling.

Support marine protected areas and sustainable fisheries management. Protecting predator populations and limiting fishing pressure are essential for long-term kelp recovery.

Most importantly, support climate action. All the restoration work in the world won’t save kelp forests if oceans keep warming beyond their temperature tolerance. Reducing carbon emissions is the only real long-term solution. Restoration buys time and preserves biodiversity, but it can’t substitute for addressing the root cause.

Australian kelp forests can recover in some areas if we combine urchin management, predator protection, and innovative restoration techniques. It requires sustained effort and funding, but the ecological and economic value of kelp forests justifies the investment. What we do in the next decade will determine whether Tasmania’s giant kelp forests survive or become a historical footnote.